In April 2004, two researchers, Giulio Fanti and Roberto Maggiolo, both from the University of Padua in Italy, reported finding a faint second face on the backside of the cloth. The findings were published in Journal of Optics (April 14, 2004), a peer-reviewed scientific journal.
The second face, found in photographs taken of the back of the cloth in 2002, was an important discovery because it all but rules out artistic methods.
The image was discovered using advanced image enhancement techniques. This was necessary because the image was very faint and concealed among the visual background noise. The most prominent background noise cloaking the details is the pattern of random plaid.
Researchers have discovered that these patterns are caused by alternating bands of darker and lighter threads in the cloth. Ancient linen was often manufactured by bleaching the thread in batches before weaving, thus producing nonuniform whiteness in the cloth.
The backside of the cloth is not available for chemical analysis. Nonetheless, scientists are convinced that the image is formed in the same way as the front side image: a chemical change to the shroud's sugar coating.
In early 2005, additional studies were done using photographs of the backside of the cloth.
